Field
Implementations of the present disclosure generally relate to planarization of surfaces on substrates and on layers formed on substrates, including an apparatus for in-situ temperature control during polishing, and methods of using the same. More specifically, implementations of the present disclosure relate to in-situ temperature control with a condensed gas during a chemical-mechanical polishing (CMP) process.
Description of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a substrate. The substrate may be a semiconductor substrate or a glass substrate. As layers of material are sequentially deposited on and removed from the substrate, the uppermost surface of the substrate may become non-planar and call for planarization and/or polishing before further patterning. Planarization and polishing are procedures where previously deposited material is removed from the feature side of a substrate to form a generally even, planar, or level surface. Planarization and polishing are useful in removing unwanted surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess material deposited to fill the features, and to provide an even surface for subsequent patterning processes.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique useful in removing unwanted surface topography, or in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing. In conventional CMP techniques, a substrate carrier or polishing head mounted on a carrier assembly positions a substrate secured therein in contact with a polishing pad mounted on a platen in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate against the polishing pad. An external driving force moves the polishing pad relative to the substrate. Thus, the CMP apparatus creates polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a polishing composition, or slurry, to affect both chemical activity and mechanical activity. This polishing or rubbing movement generates heat. Because the polishing pad is generally constructed of a polymer with poor thermal conductivity and the substrate is forced against the polishing pad by a polymer membrane in the carrier assembly, the heat generated increases the temperature of the substrate during the polishing process. High and unstable temperatures can lead to removal rate variations over time and across the wafer, which will affect the ability to control the final thickness of the material at the end of the process. In addition, for many CMP processes, higher temperatures will degrade the planarization efficiency, selectivity, or both leading to poor topography and within die planarization.
One conventional method of maintaining a stable temperature during CMP involves cooling the platen with chilled fluid via channels in the platen. However, the insulating nature of the polishing pad positioned between the substrate and the platen reduce the effectiveness of this approach. Another conventional method involves adding water or misting water to the platen to remove heat via conduction or evaporation. Dilution of the polishing slurry with water reduced the polishing rate. Removal of water from the polishing slurry is often difficult and expensive and runs the risk of drying the pad, leading to substrate defect issues.
Therefore, there is a need in the art for a method and apparatus for improved in-situ temperature control during a CMP process.